Brain

The encephalon, together with the spinal cord, forms the central nervous system. Located within the cranium, it gives rise to twelve pairs of cranial nerves that ensure the innervation of the head, certain cervical muscles, and various thoracic and abdominal viscera. Its surface presents multiple prominences and elevations.

Histologically, the encephalon is composed of billions of neurons and glial cells, organized into gray matter and white matter. In some regions, particularly within the brainstem, gray and white matter intermingle to form the reticular formation.

During embryonic development, the encephalon derives from three enlargements of the anterior neural tube: the prosencephalon, mesencephalon, and rhombencephalon. These further differentiate into five primary divisions: telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon. In the adult, three major parts are distinguished: the cerebrum (telencephalon), the cerebellum (dorsal part of the metencephalon), and the brainstem, which encompasses the remaining subdivisions.

Encephalic morphology varies across species: dogs and cats exhibit a relatively well-developed brain, while equids and bovines possess a more elongated brain with a large cerebellum. In humans, the encephalon is characterized by the highly developed cerebral cortex.